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authorJarek Poplawski <jarkao2@gmail.com>2009-07-07 19:39:16 -0700
committerDavid S. Miller <davem@davemloft.net>2009-07-08 10:46:45 -0700
commit345aa031207d02d7438c1aa96ed9315911ecd745 (patch)
treee9003cc0010b081eb975e209baa2753e8996582a /net/packet/Makefile
parent64c8165b44a91c09b19afb4110610ed242286639 (diff)
ipv4: Fix fib_trie rebalancing, part 4 (root thresholds)
Pawel Staszewski wrote: <blockquote> Some time ago i report this: http://bugzilla.kernel.org/show_bug.cgi?id=6648 and now with 2.6.29 / 2.6.29.1 / 2.6.29.3 and 2.6.30 it back dmesg output: oprofile: using NMI interrupt. Fix inflate_threshold_root. Now=15 size=11 bits ... Fix inflate_threshold_root. Now=15 size=11 bits cat /proc/net/fib_triestat Basic info: size of leaf: 40 bytes, size of tnode: 56 bytes. Main: Aver depth: 2.28 Max depth: 6 Leaves: 276539 Prefixes: 289922 Internal nodes: 66762 1: 35046 2: 13824 3: 9508 4: 4897 5: 2331 6: 1149 7: 5 9: 1 18: 1 Pointers: 691228 Null ptrs: 347928 Total size: 35709 kB </blockquote> It seems, the current threshold for root resizing is too aggressive, and it causes misleading warnings during big updates, but it might be also responsible for memory problems, especially with non-preempt configs, when RCU freeing is delayed long after call_rcu. It should be also mentioned that because of non-atomic changes during resizing/rebalancing the current lookup algorithm can miss valid leaves so it's additional argument to shorten these activities even at a cost of a minimally longer searching. This patch restores values before the patch "[IPV4]: fib_trie root node settings", commit: 965ffea43d4ebe8cd7b9fee78d651268dd7d23c5 from v2.6.22. Pawel's report: <blockquote> I dont see any big change of (cpu load or faster/slower routing/propagating routes from bgpd or something else) - in avg there is from 2% to 3% more of CPU load i dont know why but it is - i change from "preempt" to "no preempt" 3 times and check this my "mpstat -P ALL 1 30" always avg cpu load was from 2 to 3% more compared to "no preempt" [...] cat /proc/net/fib_triestat Basic info: size of leaf: 20 bytes, size of tnode: 36 bytes. Main: Aver depth: 2.44 Max depth: 6 Leaves: 277814 Prefixes: 291306 Internal nodes: 66420 1: 32737 2: 14850 3: 10332 4: 4871 5: 2313 6: 942 7: 371 8: 3 17: 1 Pointers: 599098 Null ptrs: 254865 Total size: 18067 kB </blockquote> According to this and other similar reports average depth is slightly increased (~0.2), and root nodes are shorter (log 17 vs. 18), but there is no visible performance decrease. So, until memory handling is improved or added parameters for changing this individually, this patch resets to safer defaults. Reported-by: Pawel Staszewski <pstaszewski@itcare.pl> Reported-by: Jorge Boncompte [DTI2] <jorge@dti2.net> Signed-off-by: Jarek Poplawski <jarkao2@gmail.com> Tested-by: Pawel Staszewski <pstaszewski@itcare.pl> Signed-off-by: David S. Miller <davem@davemloft.net>
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